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7<TITLE>Perfect Hash Function Generator - 6  Known Bugs and Limitations with gperf</TITLE>
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14<H1><A NAME="SEC24" HREF="gperf_toc.html#TOC24">6  Known Bugs and Limitations with <CODE>gperf</CODE></A></H1>
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16<P>
17The following are some limitations with the current release of
18<CODE>gperf</CODE>:
19
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24
25The <CODE>gperf</CODE> utility is tuned to execute quickly, and works quickly
26for small to medium size data sets (around 1000 keywords).  It is
27extremely useful for maintaining perfect hash functions for compiler
28keyword sets.  Several recent enhancements now enable <CODE>gperf</CODE> to
29work efficiently on much larger keyword sets (over 15,000 keywords).
30When processing large keyword sets it helps greatly to have over 8 megs
31of RAM.
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35The size of the generate static keyword array can get <EM>extremely</EM>
36large if the input keyword file is large or if the keywords are quite
37similar.  This tends to slow down the compilation of the generated C
38code, and <EM>greatly</EM> inflates the object code size.  If this
39situation occurs, consider using the <SAMP>&lsquo;-S&rsquo;</SAMP> option to reduce data
40size, potentially increasing keyword recognition time a negligible
41amount.  Since many C compilers cannot correctly generate code for
42large switch statements it is important to qualify the <VAR>-S</VAR> option
43with an appropriate numerical argument that controls the number of
44switch statements generated.
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48The maximum number of selected byte positions has an
49arbitrary limit of 255.  This restriction should be removed, and if
50anyone considers this a problem write me and let me know so I can remove
51the constraint.
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